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Many authors have described an increase in total serum IgE values during the first few months of immunotherapy (IT), followed by a subsequent decrease.

In previous studies in patients undergoing medium-term IT, we detected an IgE synthesis suppressor factor (SF), which was modified during the course of IT. In this study, we investigated the influence of long-term IT on the production of SF and the lymphocyte response to its stimulus. Mixed bidirectional cultures of lymphocytes isolated from healthy individuals (n = 62) and allergic patients (n = 98) were carried out after different periods of IT. The resulting supernatants were subjected to affinity chromatography, from which two fractions were obtained: the first one, likely to contain SF, was added to lymphocyte cultures from 13 allergic patients undergoing no IT (LyG1) and 6 allergic patients with > 3 years of IT (LyG5), in order to assess its inhibitory effect on IgE synthesis. We found that patients undergoing IT for > 3 years presented a significant increase in SF production and an important lymphocyte response to exogenous SF from most of the groups studied, but little response to their own SF.

These results could be ascribed to an alteration in the quantity and/or structure of the lymphocyte receptors likely to be sensitive to these factors induced by IT.